This invention is concerned with the application of sprayed fluid to surfaces of an object such as a moving web, and is more particularly concerned with apparatus that includes a pair of vertically separated spray generating units for applying fluid to opposite surfaces of a web that moves horizontally between the units, and with the control of spray patterns.
Commonly owned U.S. Pat. No. 5,314,119 granted May 24, 1994 (incorporated herein by reference) discloses and claims apparatus for applying thin coatings of fluid droplets to an adjacent surface by the use of a pick-up roll rotating in a supply of fluid and a rotating brush roll. The two rolls counter-rotate with an interference between them, so that bristles of the brush roll are bent as their tips pick up droplets of fluid. After passing out of interference, the bristles snap away from the pick-up roll and project a spray of droplets against a surface of an object to be coated, e.g., a moving web. Coating uniformity is ensured by the use of elements such as a family of windage dams and seals, baffles, blades and mist eliminators, and by the use of a brush roll with a slight spiral. Two fixed shields, one at each end of the spray pattern, isolate the spray pattern from cross currents. The length of the spray pattern laterally of a moving web is controlled by the length of the brush roll and pick-up roll.
In a specific embodiment disclosed in the aforesaid patent, the spray is directed horizontally for application to one surface of a vertically moving web, but re-arrangement of the pick-up roll, the brush roll and accompanying parts would permit the spray to be directed to a non-vertically-moving web, such as a web that is moving horizontally. However, even with such re-arrangement the spray would still be applied to only one surface of the web, and the length of the spray pattern laterally of the web would still be determined by the length of the pick-up and brush rolls.
There is a need for applying sprayed fluid simultaneously to opposite surfaces of a moving web, especially a web moving horizontally, and for applying sprayed fluid selectively to a top side or a bottom side of a horizontally moving web. Previous spray generating units, such as the spray generating unit of the aforesaid patent, have applied spray to the full width of a moving web. There is a need for applying sprayed fluid to less than the full width of a moving web and to webs of various widths, such as webs that are narrower than the spray pattern. The present invention satisfies all such needs.
A preferred embodiment of the invention uses a duplex machine in which two spray generating units are provided, spaced one above the other, with an object to be sprayed, such as horizontally moving web, between the units. An upper unit sprays downwardly onto an upper surface of the web, and a lower unit sprays upwardly onto a lower surface of the web.
Each spray generating unit has a pair of cut-offs that intercept end portions of the spray pattern from that unit and that are adjustable to control the length of the spray pattern laterally of the web, thereby to accommodate different web widths, for example. The sprayed fluid that is intercepted by the cut-offs is collected in a receptacle, from which it may be re-circulated.
The spray generating units can be operated at the same time or selectively. The cut-offs of each pair are preferably adjustable toward one another to a position at which a spray emission opening of the associated spray generating unit is blocked, so that when a spray generating unit is not in operation, internal parts are protected from external contaminants. A single spray generating unit can be employed when the ability to spray opposite surfaces of an object is unimportant.